Browsing by Subject "Fisheries"

Now showing 1 - 5 of 5
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    Accommodating dynamic oceanographic processes and pelagic biodiversity in marine conservation planning
    (Public Library of Science, 2011) Grantham, Hedley S; Game, Edward T; Lombard, Amanda T; Hobday, Alistair J; Richardson, Anthony J; Beckley, Lynnath E; Pressey, Robert L; Huggett, Jenny A; Coetzee, Janet C; Van der Lingen, Carl D
    Pelagic ecosystems support a significant and vital component of the ocean's productivity and biodiversity. They are also heavily exploited and, as a result, are the focus of numerous spatial planning initiatives. Over the past decade, there has been increasing enthusiasm for protected areas as a tool for pelagic conservation, however, few have been implemented. Here we demonstrate an approach to plan protected areas that address the physical and biological dynamics typical of the pelagic realm. Specifically, we provide an example of an approach to planning protected areas that integrates pelagic and benthic conservation in the southern Benguela and Agulhas Bank ecosystems off South Africa. Our aim was to represent species of importance to fisheries and species of conservation concern within protected areas. In addition to representation, we ensured that protected areas were designed to consider pelagic dynamics, characterized from time-series data on key oceanographic processes, together with data on the abundance of small pelagic fishes. We found that, to have the highest likelihood of reaching conservation targets, protected area selection should be based on time-specific data rather than data averaged across time. More generally, we argue that innovative methods are needed to conserve ephemeral and dynamic pelagic biodiversity.
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    Marine biodiversity in South Africa: an evaluation of current states of knowledge
    (Public Library of Science, 2010) Griffiths, Charles L; Robinson, Tamara B; Lange, Louise; Mead, Angela
    Continental South Africa has a coastline of some 3,650 km and an Exclusive Economic Zone (EEZ) of just over 1 million km 2 . Waters in the EEZ extend to a depth of 5,700 m, with more than 65% deeper than 2,000 m. Despite its status as a developing nation, South Africa has a relatively strong history of marine taxonomic research and maintains comprehensive and well-curated museum collections totaling over 291,000 records. Over 3 million locality records from more than 23,000 species have been lodged in the regional AfrOBIS (African Ocean Biogeographic Information System) data center (which stores data from a wider African region). A large number of regional guides to the marine fauna and flora are also available and are listed. The currently recorded marine biota of South Africa numbers at least 12,914 species, although many taxa, particularly those of small body size, remain poorly documented. The coastal zone is relatively well sampled with some 2,500 samples of benthic invertebrate communities have been taken by grab, dredge, or trawl. Almost none of these samples, however, were collected after 1980, and over 99% of existing samples are from depths shallower than 1,000 m--indeed 83% are from less than 100 m. The abyssal zone thus remains almost completely unexplored. South Africa has a fairly large industrial fishing industry, of which the largest fisheries are the pelagic (pilchard and anchovy) and demersal (hake) sectors, both focused on the west and south coasts. The east coast has fewer, smaller commercial fisheries, but a high coastal population density, resulting in intense exploitation of inshore resources by recreational and subsistence fishers, and this has resulted in the overexploitation of many coastal fish and invertebrate stocks. South Africa has a small aquaculture industry rearing mussels, oysters, prawns, and abalone--the latter two in land-based facilities. Compared with many other developing countries, South Africa has a well-conserved coastline, 23% of which is under formal protection, however deeper waters are almost entirely excluded from conservation areas. Marine pollution is confined mainly to the densely populated KwaZulu-Natal coast and the urban centers of Cape Town and Port Elizabeth. Over 120 introduced or cryptogenic marine species have been recorded, but most of these are confined to the few harbors and sheltered sites along the coast.
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    Patterns of distribution and spatial indicators of ecosystem change based on key species in the Southern Benguela
    (Public Library of Science, 2016) Watermeyer, Katherine E; Hutchings, Laurence; Jarre, Astrid; Shannon, Lynne J
    Several commercially and ecologically important species in the southern Benguela have undergone southward and eastward shifts in their distributions over previous decades, most notably the small pelagic fish sardine Sardinops sagax and anchovy Engraulis encrasicolus . Understanding these changes and their implications is essential in implementing an ecosystem approach to fisheries in the southern Benguela and attempting to appreciate the potential impacts of future environmental change. To investigate possible impacts of these shifts at an ecosystem level, distribution maps for before (1985-1991), during (1997-2000) and after (2003-2008) the shift in small pelagic fish were constructed for 14 key species from catch and survey data, and used to calculate spatial indicators including proportion east and west of Cape Agulhas, relative overlap in biomass and area, index of diversity, connectivity. Potential interactions on the south and west coasts were also compared. For several species (redeye; chub mackerel; kingklip; chokka squid; yellowtail), previously unidentified increases in the proportion of biomass east of Cape Agulhas were shown to have occurred over the same period as that of small pelagic fish, although none to the same degree. On average, overlap with small pelagic fish increased over time and overall system connectivity was lowest in the intermediate period, possibly indicating a system under transition. Connectivity declined over time on the west coast while increasing on the east coast. Distributions of other species have changed over time, with the region east of Cape Agulhas becoming increasingly important in terms of potential trophic interaction. Variations in distribution of biomass and structural complexity affect the trophic structure and hence functioning of the system, and implications should be considered when attempting to identify the possible ecosystem impacts of current and future system-level change.
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    Towards strengthening and harmonising: fisheries governance and legal frameworks in the Southern African 'Developing Countries (SADC) in an effort to combat illegal, unregulated and unreported (IUU) fishing in the region
    (2010) Mugjenkar, Abeeda; Feris, Loretta
    Illegal, Unreported and Unregulated (IUU) fishing is one of the most serious threats to the sustainable exploitation of living aquatic resources, jeopardizing the very foundation upon which legislation and policies are based the world over and the global efforts to promote better ocean and governance. IUU fishing also represents a major hazard to the marine environment, the sustainability of fish stocks and marine biodiversity. International, regional, national organizations and governments have been tremendously active in the fight against IUU fishing over decades, some achieving success and others failing dismally. In 2001, the Food and Agriculture's Organization of the United Nations (FAQ's) adopted an International Plan of Action on IUU fishing (the IPOA-IUU) to prevent, deter and eliminate IUU fishing.1 The IPOA-IUU2 is a voluntary instrument which aims at preventing, deterring and eliminating IUU fishing by providing countries with a set of comprehensive, effective and transparent measures on the basis of which they may act either directly or through relevant Regional Fisheries Management Organizations (RFMOs).3 The· IPOA-IUU seek to address IUU fishing in a holistic manner and provide a comprehensive 'toolbox' as a checklist so that States4 can select those measures that are most relevant to their particular situations. The implementation of the IPOA-IUU focuses on the elaboration of national plans of action on seven types of measures such as coastal State measures, port State measures, and market related measures.
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    Variability in the diet of cape fur seals and their interaction with fisheries off the South African coast, 2010-2019
    (2025) Gumede, Nosipho Clementine; Ryan, Peter
    Cape fur seals (Arctocephalus pusillus pusillus) are sentinel marine top predators in southern African coastal waters due to their generalist diet and wide breeding range from southern Angola (Baia dos Tigres) to Algoa Bay, South Africa. Their long-life span makes them good indicators of ecosystem health by providing insights on ecological interactions in the food webs of the South African marine ecosystem, and on the variation in the availability of prey resources. This dissertation describes the diet of Cape fur seals off the South African coast between 2010 and 2019 based on the analysis of scats collected at 11 South African colonies from Kleinsee (29°39' S, 17°04' E) to Robberg Ledges (34º03' S, 23º22' E). The colonies were divided into three geographical regions: St Helena Bay, Saldanha Bay to Cape Agulhas, and east of Cape Agulhas. Potential competition for prey fish between the Cape fur seal and fishery catches was also investigated. Catches by the purse-seine fishery landed at Lambert's Bay, Saldanha Bay and Gansbaai were compared with the diet of fur seals at nearby colonies (Lambert's Bay, Jutten Island and Geyser Rock, respectively). The importance of small pelagic fish in the Cape fur seal diet also was compared to acoustic biomass estimates of these key fish species. A total of 4165 scat samples were used to infer spatial and temporal variation in the Cape fur seal diet. Fish otoliths, cephalopod beaks and seabird feathers were used to identify prey to the lowest taxonomic level possible, and the mass and length of fish prey were estimated from otolith lengths using regression equations. Fifty-three prey taxa (43 fish, 6 cephalopods, 4 seabirds) were identified from scats, and indices of relative importance (%IRI), mass contribution (%M), numerical abundance (%NA), and frequency of occurrence (%FO) were used to determine the importance of each prey taxon to the diet. Fish dominated the diet (88.0%FO) followed by seabirds (9.1%FO), cephalopods (5.5%FO) and crustaceans (0.4%FO). In decreasing order of importance and in terms of %NA, the most important prey species were anchovy (Engraulis encrasicolus capensis), horse mackerel (Trachurus trachurus capensis), sardine (Sardinops sagax) and hake (Merluccius capensis and M. paradoxus). Anchovy dominated the diet across all study areas and years, while other species varied in importance over the study years. There was seasonal variation in the diet across all three regions, with anchovy being consumed more during winter (non-upwelling season) than summer. Almost all other fish taxa were consumed more during summer in all the three study regions. Larger prey such as hake and horse mackerel contributed less to the diet; in terms of mass contribution (10.9%M and 10.3%M, respectively) than the smaller anchovies and sardines (combined 68.8%M). Scat samples were compared with stomach content samples obtained from 1974 to 1996. There were no changes in diet composition (fish, cephalopods, crustaceans, seabirds) between the different study periods or the different diet analysis methods. However, there were changes in proportions of prey type consumed; seabirds were consumed less during 1974 - 1996 compared with 2010 to 2019. Pelagic goby (Sufflogobius bibarbatus) (55.0%NA) dominated the diet in 1974 – 1996, while anchovy (67.6%NA) predominated in 2010– 2019. Only 30 prey taxa (22 fish, 5 cephalopods, 2 crustaceans, 1 seabird) were identified from 2 336 stomach content samples, compared with 53 from scats. Although there is some uncertainty due to the different methods, it seems that prey proportions have changed between the two periods. Among the commercial targeted pelagic species (i.e. sardine and horse mackerel), Cape fur seals and purse-seine fisheries mainly targeted juvenile to adult fish, except for anchovy, where fisheries caught much smaller fish. There was an overlap in fish size distribution (50 – 200 mm) of sardine and red-eye (Etrumeus whiteheadi) found in seal scats and commercial landings records. A positive correlation was found between spawner acoustic biomass estimates and the importance (%NA) of anchovy and sardine in the Cape fur seal diet. The importance of sardine decreased in contribution when biomass estimates were low. Similarly, anchovy importance in the diet was positively correlated with biomass estimates. However, the overall consumption of anchovy did not correlate with the estimated biomass, but there was correlation between sardine consumption and the biomass estimate. Cape fur seals seemingly could switch between prey depending on the available biomass. This was evident in the study colonies and during the study periods. This study demonstrates that the diet of Cape fur seal has remained relatively unchanged since 1974. They have largely increased the proportions of species they consume based on abundance. The consistent presence of anchovy in the diet of Cape fur seals over time suggests that this fish species constitutes an important food item for fur seals. In general, there was no competition between the purse-seine fishery and Cape fur seals. The difference in anchovy sizes caught by the fishery (45 – 130 mm) and seals (17 – 250 mm) indicate that there may be less competition than previously thought. However, purse-seine fishery and seals both target similar sizes (21.9 – 250 mm) of red eye and sardine. Increases in the presence of seabirds in the diet since 1974 have implications for three species of Endangered seabirds: African Penguins (Spheniscus demersus), Cape Gannets (Morus capensis) and Cape Cormorants (Phalacrocorax capensis). Overall, the study demonstrated some long-term changes in the diet of Cape fur seals over the past 40 years despite the use of two different sampling methods and the spatially patchy data.